GMRT observations of the exoplanetary systems $\tau$ Bo\"otis and 55 Cancri

Abstract

We present archival Giant Metrewave Radio Telescope (GMRT) observations of two exoplanetary systems, $\tau$ Bo\"otis, and 55 Cancri, at 610 MHz and 150 MHz, respectively. Theoretical models predict these systems to have some of the highest expected flux densities at radio wavelengths. Both $\tau$ Bo\"otis and 55 Cancri have been previously observed at low frequency ($\sim$ 30 MHz) with Low-Frequency Array (LOFAR) (Turner et al. 2020). $\tau$ Bo\"otis shows tentative signatures of circularly polarized emission at 30 MHz, while no emission was detected from 55 Cancri. We do not detect radio emission from both the systems, but the GMRT observations set $3\sigma$ upper limits of 0.6 mJy at 610 MHz for $\tau$ Bo\"otis and 4.6 mJy at 150 MHz for 55 Cancri. The sensitivity achieved at 610 MHz in these observations is comparable to some of the deepest images of an exoplanet field.